In a nationally representative Canadian survey, cannabis use appeared to weaken the association between PTSD and both severe depression and suicidal ideation.
PTSD researchers, mental health clinicians, and policy makers considering cannabis for PTSD treatment.
Cannabis use weakened the PTSD-depression and PTSD-suicidal ideation link
What the researchers found
Among 24,089 respondents in the Canadian Community Health Survey, people with PTSD who used cannabis had lower odds of experiencing a major depressive episode and suicidal ideation compared to those with PTSD who did not use cannabis, after controlling for demographics and comorbidities.
Why it matters
PTSD dramatically increases the risk of depression and suicide. If cannabis genuinely moderates this relationship, it could have significant implications for treatment, though observational data alone cannot prove causation.
The numbers in context
24,089 respondents; 420 (1.7%) had PTSD; 28.2% of those with PTSD used cannabis vs. 11.2% without PTSD; cannabis use associated with reduced odds of depression and suicidal ideation in PTSD group.
How the study worked
Cross-sectional analysis of the 2012 Canadian Community Health Survey-Mental Health (n=24,089) using logistic regression with interaction terms for cannabis and PTSD status.
What this study cannot tell us
Cross-sectional design cannot establish causation; self-reported data; cannabis use patterns (frequency, type) were not detailed; potential for residual confounding; PTSD sample relatively small.
How to read the evidence
Moderate: large nationally representative sample with appropriate statistical controls, but cross-sectional design limits causal inference.
When this study was published
Published 2020.
The bigger picture
This population-level finding aligns with growing clinical interest in cannabinoids for PTSD treatment. However, the cross-sectional design means self-medication cannot be distinguished from therapeutic benefit.
Questions still open
- Would longitudinal data confirm a protective effect? Which cannabis types or patterns of use might explain this association?
Common questions
Did cannabis reduce PTSD symptoms directly?
Does this prove cannabis treats PTSD-related depression?
Read the original research
Does cannabis use modify the effect of post-traumatic stress disorder on severe depression and suicidal ideation? Evidence from a population-based cross-sectional study of Canadians.
Journal of psychopharmacology (Oxford, England), 34(2), 181-188
Citation
Lake, Stephanie; Kerr, Thomas; Buxton, Jane; Walsh, Zach; Marshall, Brandon Dl; Wood, Evan; Milloy, M-J. (2020). Does cannabis use modify the effect of post-traumatic stress disorder on severe depression and suicidal ideation? Evidence from a population-based cross-sectional study of Canadians.. Journal of psychopharmacology (Oxford, England), 34(2), 181-188. https://doi.org/10.1177/0269881119882806
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